Now to new developments in a bizarre case of a woman convicted of killing her 4-year-old foster son by poisoning him with salt. The story is the focus of today's episode of "katie." Paula faris joins us now with the brand new interview with the woman behind bars. It's a story we have been covering on "20/20." Could a woman with no history of violence, mental health issues, not so much as a traffic ticket, suddenly snap? Hannah overton is serving a life sentence for killing her foster son. She's always maintained her innocence. I wholeheartedly believe my innocence will be prove and I'll be home. Reporter: Six years ago, hannah and her husband, larry, welcomed foster child andrew into their home. For the last five years, hannah has been behind bars after being found guilty of poisoning the 4-year-old child with a high amount of sodium. She continues to fight back from jail and maintain her innocence. Did you kill your foster child, a andrew burd? No. Reporter: Did you ever think about harming him in any way? No. Reporter: She s andrew seemed to adjust well. But she soon noticed strange behaviors. He would try to eat the soap, shampoo, cat food, dog food. Rep IT WAS SUGGESTED HE May have pica, a bizarre eating disorder. One day after eating soup sprinkled with zatarain's creole seasoning, he stumbled to the floor. He said he was cold. I thought he had a stomach virus. Reporter: They rushed him to urgent care. Just regards from the place, he stopped breathing. She forced him to have 23 tea spoons of hot person and then watching him die in agony for 2 1/2 hours. Reporter: She was found guilty of capital murder. Now her five children are growing up without their mother. I didn't say good-bye to the kids in the morning because i thought it was finally going to be over. Reporter: Hannah has spent five years in a maximum security pridsen. She's allowed absolutely no physical contact with her five children. Her fate is in the texas court of criminal appeals. They could rule any day.

This transcript has been automatically generated and may not be 100% accurate.

Now Playing: Attempting to Recreate the Sound Experiment from the Mark Carver Case

Now Playing: Deadly Chain of Car Crashes on Icy I-96 Kills at Least 2

Now Playing: {{itm.title}}

{"id":17480287,"title":"Woman Convicted of Salt-Poisoning to Appear on 'Katie'","duration":"3:00","description":"Katie Couric will have new interview with mom convicted of killing foster son.","url":"/GMA/video/katie-preview-hannah-overton-convicted-salt-poisoning-adopted-17480287","section":"GMA","mediaType":"default"}